The long-term goal of the proposed research project is to characterize the factors and processes responsible for establishment of the mammalian epigenome, then decipher the mechanisms by which aberrations in epigenetic reprogramming which occur during preimplantation embryo development result in failed development or disease. Two key factors are associated with the epigenetic control of gene expression 1) DNA methylation and 2) histone modifications. Shortly after fertilization mammalian embryos undergo genome-wide epigenetic reprogramming by demethylation followed later by de novo remethylation. Aberrant epigenetic reprogramming has been clearly linked to failed embryo development and associated with serious human diseases. From the standpoint of human reproductive health and human disease, understanding the factors and mechanisms which control epigenetic reprogramming during early mammalian development is of critical importance. The objective of the proposed research is to generate scientific information that can be used to address these concerns. We propose to use a bovine model to pursue the following aims. Specific Aim 1 is to characterize the expression and activity of DNA methyltransferases (DNMTs), histone methyltransferases (HMTs) and their associated genes during mammalian oocyte maturation and pre-implantation development. Expression of genes coding for these enzymes in addition to protein quantity, localization and trafficking will be analyzed in bovine ova and embryos. Specific Aim 2 is to silence the expression of DNMTs and HMTs during bovine preimplantation development, then determine the effect on epigenetic reprogramming and embryo/fetal development. For study 1, RNA interference (RNAi) will be used transiently knock down expression of DNMTs and HMTs at the 1-cell stage of development. The percentage of embryos developing in vitro and embryo quality will be assessed. Global methylation in addition to methylation of specific target genes will also be analyzed. Microarray analysis and quantitative real-time PCR will be utilized to identify alterations in gene expression resulting from RNAi induced gene silencing. Immunocytochemistry will be employed to assess changes in protein. In a second study, siRNAs designed to silence the expression of DNMTs, HMTs and/or associated genes will be injected into one-cell bovine embryos which wil then be cultured to the blastocyst stage. These will be transferred into recipient females. Pregnancy rates will be compared between treatments and the normalcy of fetal development monitored by ultrasound. Conceptuses will be removed at 60 days of gestation to perform an extensive morphological and molecular analysis of placental and fetal tissues using methods similar to those described for study 1. Information generated in the proposed studies will be useful for generating guidelines and strategies to improve methods for assisted reproduction in humans, prevention of reproductive failure in addition to the prevention of human disease.